The novel process of this invention is particularly useful for preparing an intermediate .alpha.-iodo-, or .alpha.-bromo-amide which is readily dehydrohalogenated to an .alpha.,.beta.-unsaturated amide.
Where the amide is a saturated azasteroid, this novel process greatly facilitates the production of the .DELTA.-1 azasteroid which is useful as a potent inhibitor of testosterone 5-.alpha.-reductase [see Nayfe et al., Steroids, 14, 269 (1969); Voigt and Hsia, Endocrinology, 92, 1216 (1973); Canadian Pat. No. 970,692]. In this regard, known methods for introduction of the .DELTA.-1 double bond into azasteroids include selenic anhydride oxidation [Back, T. G., J. Org. Chem., 46, 1442 (1981); Rasmussen et al., J. Med. Chem. 29, 2298 (1986)], sulfoxide elimination [U.S. Pat. Nos. 4,377,584; 4,220,775], a complicated 5-step dehydrogenation involving a sulfenate intermediate [Magnus et al., J. Am. Chem. Soc. 108, 221 (1986)], and silylation mediated DDQ (2,3-dichloro-5,6-dicyano-1,4-benzoquinone) oxidation [Bhattacharya et al., J. Am. Chem. Soc. 110, 3318 (1988)].
The process of the instant invention avoids some of the disadvantages present in the prior art methods which include poor yields, expensive reagents, unwanted by-products, and the use of toxic selenium catalysts.